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I have a 2003 cayenne turbo that developed this sudden and intermittent coolant leak and hoping the wisdom of the forum members can give me some advice. The vehicle had the aluminum coolant pipes and replacement T pipes placed about 4 years ago. I replaced the coolant reservoir cap with part 1J0121321B about 2 years ago. My coolant reservoir is 7L0121407C which I am assuming is the original reservoir given the part number starting with 7L0. This last week, I took a couple long trips on the highway in 80 degree weather and upon arriving home today after a 3 hour drive, as soon as I got out of the car there was a sudden pouring of coolant from the behind the passenger wheel well. I went to remove the coolant reservoir cap and depressurizing the system seem to get it to slow down and stop but I did also notice a sudden drop in the coolant level in the reservoir. I filled the reservoir up and took it for another drive later in the day with the car at operating temperature and when I stopped the car again, some fluid at a slower rate started dripping again from behind the passenger wheel well, stopping by removing the reservoir valve. On both occasions, I looked under to hood and around all the reservoir hose connections and top of reservoir around its seal and did not see any obvious leaking or wetness. After doing some research on this forum, it has been suggested that it could be a bad reservoir cap or leaking reservoir. Could it be leaking on the underside of the reservoir that I cannot visualize or are there other coolant parts in this area that could be leaking when the car is shut off. I do not see any leaking with the car is running and the coolant gauge remains at the middle which I would guess means the water pump is fine. If it just needs a reservoir replacement, I can easily do that but don't want to just throw parts at fixing it if unsure of the problem.

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I too have a 2003 CTT and have had my reservoir tank split at the seams every 90,000 km on average.


If you haven’t replaced your reservoir tank yet, there is a good chance the reservoir is the source of your leak.


The plastic coolant Ts were rupturing every 90,000 km as well.


I’ve replaced the Ts with stainless hoping not to have them fail again.


There is also the electric coolant pump for turbo oil cooling when engine is turned off that could possibly be leaking. It is situated in the wheel well. Mine has not leaked as yet.

Edited by bigbuzuki
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